USMLE - Microbiology

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virulence factor of staph aureus - binds Fc-IgG, inhibiting complement fixation and phagocytosis: protein A
superantigen that binds to MHC II and TCR, resulting in polyclonal T cell activation: TSST - (staph aureus)
what makes coagulase?: staph aureus
antibody to what enhances host defenses against strep pyogenes?: M protein
group A beta-hemolytic strep?: strep pyogenes
what detects recent strep pyogenes infections?: ASO titer
associated with rusty sputum, sepsis in sickle cell, and splenectomy?: strep pneumo
most common cause of meningitis, otitis, pneumonia, sinusitis?: strep pneumo
what gives immunity to strep pneumo?: IgG antibodies to surface acidic polysaccharide
causes pneumonia, meningitis, and sepsis mainly in babies: group B strep (agalactiae) - beta hemolytic, bacitracin resistant
what is Lancefield grouping based on?: differences in the C carbohydrate on the bacterial cell wall
what can grow in 6.5% NaCl: enterococci
enterococci can cause what?: UTI, subacute endocarditis, biliary tract infections
bacteria related to colon cancer?: strep bovis
type of strep viridans that can cause subacute bacterial endocarditis?: strep sanguis
what does C. perfringens produce?: alpha toxin
gram-positive rods with metachromatic granules?: corynebacterium diphtheriae
woolsorter's disease?: bacillus anthracis
inhalation of anthrax spores?: flulike symptoms that rapidly progress to fever, pulmonary hemorrhage, and shock
gram-positive anaerobe that causes oral/facial abscesses that may drain through sinus tracks in skin: actinomyces
gram positive, weakly-acid fast aerobe that causes pulmonary infection in immunocomprimised patients: nocardia asteroides
sulfur granules: actinomyces
gram-positive rods forming long branching filaments resembling fungi: actinomyces & nocardia
most invasive disease of H. flu is caused by what capsular type?: B
treatment for H. flu meningitis?: ceftriaxone
treatment for neisseria gonorrhea?: ceftriaxone - also z pack or doxycycline because 50% will also be infected with chlamydia
why don't you want to culture if pt. has epiglottitis?: manipulation cause laryngeal spasm
members of enterobacter family (7): e. coli, salmonella, shigella, klebsiella, enterobacter, serratia, proteus
what antigen is related to the virulence of enterobacter?: K antigen
all of these ferment glucose and are oxidase negative: enterobacter
these bacteria grow pink colonies on MacConkey's agar: klebsiella, e. coli, enterobacter (KEE), citrobacter
salmonella or shigella: motile and can disseminate hematogenously?: salmonella
salmonella or shigella: which is more virulent?: shigella
salmonella or shigella: symptoms may be prolonged with antibiotic treatments: salmonella
salmonella or shigella: animal reservoir: salmonella
this is usually transmitted from pet feces, contaminated milk, or pork; outbreaks common in daycare centers: yersinia enterocolitica
this can mimic Crohn's or appendicitis & can disseminate to produce lymphadenitis: yersinia enterocolitica
arthritis can develop with yersinia infection in patients with what?: HLA-B27
vibrio parahaemolyticus and v. vulnificus: contaminated seafood
reheated rice: B. cereus
meats, mayonase, custard: s. aureus
reheated meat dishes: c. perfringens
undercooked meat: e. coli 0157:H7
poultry, meat, eggs: salmonella
bloody diarrhea; comma or S-shaped organisms: campylobacter
is campylobacter motile?: yes
e. coli producing shiga-like toxin; can cause HUS: enterohemorrhagic
day-care outbreaks, pseudoappendicitis: yersinia
protazoan causing bloody diarrhea: entamoeba histolytica
protaozoa causing watery diarrhea: giardia, cryptosporidium (in immunocompromised)
treatment for legionella?: erythromycin
UTI - urine with alkaline pH: proteus - very motile - able to break down urea
pneumonia in CF: pseudomonas
wound and burn infections: pseudomonas
treatment for pseudomonas?: amnoglycoside plus extended-spectrum penicillin (piperacillin, ticarcillin)
aerobic gram-negative rod; oxidase positive, non-lactose fermenting; pyocyanin pigment: pseudomonas
hot tub folliculitis: pseudomonas
pneumonia, sepsis, UTI, drug use and diabetic osteomyelitis: pseudomonas
cellulitis from animal bite, cats, dogs: pasteurella
dairy products, contact with animals: brucella
ghon complex: TB granulomas (Ghon focus) with lobar and perihilar LN involvement; reflects primary infection or exposure
mycobacterium scrofulaceum: cervical lymphadenitis in kids
mycobacterium kansasii: pulmonary TB-like symptoms
acid-fast bacillus that likes cold temperatures and cannot be grown in vitro: mycobacterium leprae
reservoir for m. leprae in U.S.?: armadillos
what does m. leprae infect?: skin and superficial nerves
treatment for leprosy?: long-term oral dapsone - toxicity is hemolysis and methemoglobinemia
which type of Hanson's diseaseiis worse?: lepromatous worse than tuberculoid
the chlamydial petidoglycan wall is unusual in that it lacks what?: muramic acid
treatment for chlamydia?: erythromycin or tetracycline
cytoplasmic inclusions seen on Giemsa or fluorescent antibody-stained smear: chlamydia
infection of liver capsule with RUQ pain; associated with chlamydial or gonococcal infection: Fitz-Hugh-Curtis syndrome
how do the reticulate bodies of chlamydia replicate?: binary fission
types A, B, and C of chlamydia: Africa/Blindness/Chronic infection
types D-K of chlamydia: urethritis/PID, ectopic pregnancy, neonatal pneumonia or conjunctivitis
types L1, L2, and L3 of chlamydia: lymphogranuloma venereum (acute lymphadenitis - positive Frei test)
treatment for neonate after passage through chlamydia-infected birth canal?: erythromycin eye drops
most common STD in U.S.?: chlamydia
only spirochete that can be visualized using analine dyes (Wright's or Giemsa stan) in light microscopy: borrelia
shepherd's crook-shaped spirochete: leptospira
Wal's disease: fatal from of leptospira infection - jaundice, bleeding, renal failure, skeletal muscle necrosis
treatment for Borrelia recurrentis?: doxycycline, erythromycin
treatment for Lyme disease?: doxycycline
what causes yaws?: tremonema pertenue - tropical infection that is not an STD, although VDRL test is positive
what are important reservoirs for ixodes? what is required for tick life cycle?: mice; deer
signs of tertiary syphilis?: broad-based ataxia; positive Romberg; Charcot joints; stroke without hypertension
congenital syphilis?: saber shins, saddle nose, deafness
primary syphilis?: painless chancre
secondary syphilis?: disseminated isease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata
VDRL positive, FTA positive?: active infection
VDRL positive, FTA negative?: probably false positive
VDRL negative, FTA positive?: successfully treated
VDRL false positives?: viruses (mono, hep), drugs, rhematic fever, RA, SLE, leprosy
Weil-Felix reaction?: classic test that uses cross-linking proteus antigens to confirm diagnosis of rickettsia
strep associated with pharyngitis, cellulitis, impetigo, scarlet fever, TSS, rheumatic fever, glomerulonephritis?: strep pyogenes (group A beta hemolytic)
characteristics of rheumatic fever?: subcutaneous nodules, erythema marginatum, chorea, carditis
tumbling motility, menigitis in newborns, unpasteurized milk: listeria monocytogenes
virulence factor of staph aureus?: protein A
what does c. difficile produce?: a cytotoxin, an exotoxin that kills enterocytes, causing pseudomembranous colitis
what encodes the exotoxin of corynebacterium diphtheriae?: beta-prophage
vesicular papules covered y black eschar: bacillus anthracis
what part of gram-negative bugs inhibits entry of penicillin and vancomycin?: the outer membrane layer
this vaccine contains type B capsular polysaccharide conjugated to diphtheria toxoid or other protein: h. flu
flagellar antigen of enterobacter?: H antigen
somatic antigen of enterobacter?: O antigen (polysaccharide of endotoxin)
viruses causing watery diarrhea?: rotavirus, adenovirus, norwalk virus
pertussis toxin permanently disables what?: Gi
cholera toxin permanently activates what?: Gs
how does pertussis toxin promote lymphocytosis?: by inhibiting chemokine receptors
treatment of choice for most rickettsial infections?: tetracycline
classic triad of rickettsiae?: headache, fever, rash (vasculitis)
rickettsiae are obligate intracellular parasites and need what?: CoA and NAD
all rickettsiae except what are transmitted by an arthropod vector and cause headache, fever, and rash?: coxiella
why is coxiella an atypical rickettsia?: because it is transmitted by aerosol and causes pneumonia
what causes rocky mountain spotted fever? to where is it endemic?: rickettsia rickettsii; endemic to east coast
vector for rocky mountain spotted fever?: tick; rickettsia rickettsii
vector for endemic typhus?: fleas; rickettsia typhi
vector for epidemic typhus?: human body louse; rickettsia prowazekii
what causes Q fever?: coxiella burnetii
rickettsial disease with no rash, no vector, negative Wiel-Felix, and casative organism can survive outside for a long time: coxiella burnetii
what does the Weil-Felix reaction assay for?: antirickettsial antibodies, which cross-react with proteus antigen
what is the only bacterial membrane containing cholesterol?: mycoplasma pneumoniae
growth on Eaton's agar?: mycoplasma pneumoniae
normal flora dominant in nose: staph aureus
normal flora dominant in skin: staph epidermidis
normal flora dominant in oropharynx: strep viridans
normal flora dominant in dental plaque: strep mutans
normal flora dominant in colon: bacteriodes fragilis > e. coli
normal flora dominant in vagina: lactobacillus, colonized by e. coli and group B strep
common causes of pneumonia in kids (6 wks. - 18 yrs): viruses (RSV), mycoplasma, c.pneumonia, s.pneumo
common causes of pneumonia in adults (18-40): mycoplasma, c.pneumo, s. pneumo
common causes of pneumonia in adults (40-65): s. pneumo, h. flu, anarobes, viruses, mycoplasma
common causes of pneumonia in elderly: s. pneumo, viruses, anaerobes, h.flu, g-rods
common causes of pneumonia in nosocomial: staph, gram-negative rods
common causes of pneumonia in immunocomprimised: staph, gram-negative rods, fungi, viruses, PCP (HIV)
common causes of pneumonia in aspiration: anaerobes
common causes of pneumonia in alcoholic/IV drug user: strep pneumo, klebsiella, staph
common causes of pneumonia in postviral: staph, h. flu
common causes of pneumonia in neonate: group B strep, e. coli
common causes of atypical pneumonia: mycoplasma, legionella, chlamydia
causes of meningitis in newborn (0-6 mos): GBS, e.coli, listeria
causes of meningitis in children (6 mos - 6 yrs): s. pneumo, n.meningitidis, h.flu B, enterovirus
causes of meningitis in 6-60 year olds: n.meningitidis, enterovirus, s.pneumo, hsv
causes of meningitis in elderly (over 60): s.pneumo, g-rods, listeria
causes of meningitis in HIV: cryptococcus, CMV, toxoplasmosis (brain abscess), JC virus (PML)
CSF findings in bacterial meningitis: increased pressure, neutrophils, protein - decreased sugar
CSF findings in fungal/TB meningitis: increased pressure, lymphocytes, protein - decreased sugar
CSF findings in viral meningitis: n/+pressure, + lymphocytes, normal protein and sugar
cause of osteomyelitis in most people: staph aureus
cause of osteomyelitis in sexually active: neisseria gonorrhoeae (rare), septic arthritis more common
cause of osteomyelitis in diabetics and drug addicts: pseudomonas
cause of osteomyelitis in sickle cell: salmonella
cause of osteomyelitis in prosthetic replacement: staph aureus and staph epidermidis
cause of vertebral osteomyelitis: TB (Pott's disease)
UTI in ambulatory patients: e. coli (50-80%), klebsiella (8-10%)
second most common cause of UTI in young ambulatory women: staph saprophyticus
cause of UTI in hospital?: e. coli, proteus, klebsiella, serratia, pseudomonas
UTI - colonies show metallic sheen on EMB agar: e. coli
UTI - large mucoid capsule and viscous colonies: klebsiella
UTI - swarming on agar (motility); produces urease: proteus
vaginitis, strawberry-colored mucosa: trichomonas vaginalis
noninflammatory, malodorous discharge; positive whiff test; clue cells: gardnerella vaginalis
risk factor: newborn nursery: CMV, RSV
risk factor: urinary catheterization: e. coli, proteus
risk factor: respiratory therapy equipment: pseudomonas aeruginosa
risk factor: work in renal dialysis unit: HBV
risk factor: hyperalimentation: candida albicans
risk factor: water aerosols: legionella
infections dangerous in pregnancy: ToRCHeS: toxo, rubella, CMV, HSV, HIV, syphillis
traumatic open wound: c. perfringens
surgical wound: staph aureus
sepsis/meningitis in newborn: group B strep
neutrophils in CSF?: bacterial meningitis
normal protein and sugar in meningitis?: viral
teichoic acid is unique to what type of organisms?: gram-positive
endotoxin/LPS (outer membrane) is unique to what type of organisms?: gram-negative
what do teichoic acid and lipid A induce?: TNF and IL-1
space between the cytoplasmic membrane in gram-negative bacteria: periplasm - contains many hydrolytic enzymes, including beta lactamases
this mediates adherence to surfaces, especially foreign surfaces, e.g. indwelling catheters: glycocalyx - made of polysaccharide
this contains a variety of genes for antibiotic resistance, enzymes, and toxins: plasmid - made of DNA
what is the only gram-positive with endotoxin?: listeria
what is exotoxin made of?: polypeptide
what is endotoxin made of?: lipopolysaccharide
typical diseases with exotoxin?: tetanus, botulism, diphtheria
tpical diseases with endotoxin?: meningococcemia, sepsis by gram-negative rods
gram-negative cocci?: neisseria
these have a gram-negative cell wall but are too small to be seen with light microscope: spirochetes - must be visualized with darkfield microscope
no cell wall; neither gram-positive or gram-negative: mycoplasma
lipopolysaccharide found in cell wall of gram-negative bacteria: endotoxin - heat stable
this bug inactivates elongation factor (EF-2), causes pharyngitis and pseudomembrane in throat: corynebacterium diphtheriae
ADP ribosylation of G protein stimulates adenylyl cyclase, increasing pumping of Cl- and H20 into gut: cholera
what does e. coli heat-labile toxin stimulate?: adenylate cyclase
what does e. coli heat-stable toxin stimulate?: guanylate cyclase
name the 6 classic gram-positives: strep, staph, bacillius, clostridium, corneybacterium, listeria
what does bordatella pertussis stimulate?: adenylate cyclase; also inhibits chemokine receptor
double zone of hemolysis on blood agar?: C. perfringens
what does C. tetani block the release of?: inhibitory NT glycine
what does C. botulinum block the release of?: acetylcholine
what does shiga toxin do?: cleaves host cell rRNA; also enhances cytokine release, causing HUS
what type of bugs are rickettsia and chlamydia?: intracellular parasites
neisseria meningitidis ferments what?: maltose and glucose
neisseria gonorrhea ferments what?: glucose
what produces a blue-green pigment?: pseudomonas
what produces a red pigmetn?: serratia maracescens
IgA proteases allow what organisms to colonize mucosal surfaces?: strep pneumo, neisseria meningitidis, neisseria gonorrhoeae, h. flu
silver stain?: fungi, PCP, legionella
india ink?: cryptococcus neofromans
Ziehl-Neelsen stain?: acid-fast baceria
PAS stain?: stains glycogen, mucopolysaccharides; used to diagnose Whipple's disease
Giemsa's stain?: borrelia, Plasmodium, trypanosomes, chlamydia
congo red?: amyloid; apple-green birefringence in polarized light (because of beta-pleated sheets)
chocolate agar with factors V and X?: H. influenzae
Thayer-Martin (VCN) agar?: N. gonorrhoeae
Bordet-Gengou (potato) agar?: B. pertussis
tellurite plate, Loffler's medium, blood agar?: C. diphtheriae
Lowenstein-Jensen agar?: M. tuberculosis
pink colonies on MacConkey's agar?: lactose-fermenting enterics - Klebsiella, e. coli, enterobacter (fast); citrobacer, serratia (slow)
charcoal yeast agar buffered with increased iron and cysteine?: Legionella
Sabouraud's agar?: fungi
obligate aerobes (4): Nagging Pests Must Breathe: nocardia, pseudomonas, mycobacterium, TB, bacillius
obligate anaerobes (3): clostridium, bacteriodes, actinomyces - lack catylase and/or superoxide dismutase, and thus are susceptible to oxidative damage; generally foul smelling, difficult to culture, and produce gas in tissue (CO2 and H2)
obligate intracellular bugs (2): rickettsia, chlamydia (stay inside when it's Really Cold)
facultative intracellular (8): Some Nasty Bugs May Live FacultativeLY:
: salmonella, neisseria, brucella, mycobacterium, listeria, francisella, legionella, yersinia
encapsulated bugs (4): strep pneumo, H. flu, neisseria meningitidis, klebsiella - positive quellung reaction
bacillus anthracis, c. perfringens, and c. tetani form what?: spores (gram positive soil bugs)
alpha hemolytic bacteria?: s.pneumo(cat-, optS), s.viridans (cat-, optR)
beta hemolytic bacteria?: s. aureus (cat+, coag+), GAS (cat-, bacS), GBS (cat-,bacR), listeria
how do you differentiate strep pyogenes form strep agalactiae?: strep agalactiae (bacitracin S), strep agalactiae (bacitracin R)
DNA transferred from 1 bacterium to another: conjugation
nature of DNA transferred in conjugation: chromosomal or plasmid
DNA transferred by a virus from 1 cell to another: transduction
nature of DNA transferred in transduction: any gene in generalized transduction; only certain genes in specialized transduction
purified DNA taken up by a cell: transformation (any DNA)
most capsules are made out of polysaccharide except bacillus anthracis, which contains what?: d-glutamate
chemical composition of spore?: keratin-like coat; dipicolinic acid - provides resistance to heat, dehydration, and chemicals
what is a pilus made out of?: glycoprotein
location of exotoxin genes?: plasmid or bacteriophage
location of endotoxin genes?: bacterial chromosome
which is antigenic - exotoxin or endotoxin?: exotoxin
both of these bugs activate EF-2: corynebacterium, pseudomonas (exotoxin A)
how do you distinguish staph epidermidis from staph saprophyticus: s. epidermidis is novabiacin S, s. saprophyticus is novabiacin R
another name for group A beta hemolytic strep?: strep pyogenes
another name for group B beta hemolytic strep?: strep agalactiae
which is bile soluble - strep pneumo or strep viridans?: strep pneumo

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